Small shaped metallic object



All@ 15, 1939 c. PFANSTIEHL 2,169,966

SMALL SHAPED METALLIC OBJECT Filed NOV. 28, 1958 'Patented Aug. 15, 1939l METALLIC OBJECT Carl Pfanstiehl, Highland Park, Ill., assignor toManstiehl Chemical Company, a corporatio of Illinois ApplicationNovember 28, 1938, Serial No. 242,865

1 Claim. (Cl. 29-148) This invention relates to small shaped metallicobjects and particularly to such objects not substantially over onefour-thousandth of a cubic inch in volume.

The pressing of metallic objects from powdered metallic particles is nowwell-known, but the development of suitable dies or methods for formingextremely small objects has hitherto been thought impracticable.

lo For example, the preforming of points for pen nibs', phonographneedles, meter pivots, or similar small objects, by pressing hashitherto been a very expensive process, and the objects formed by thepreviously known methods have not had l5 the uniformity of size andstructure desired.

In accordance with this invention, a method is provided for forming in avery cheap and simple manner small objects of predetermined size andshape, primarily of geometric patterns and of a uniformity of structurehitherto impossible in such small objects.

An apparatus suitable for carrying out the invention is illustrated inthe drawing, in which Fig. l is an elevation, partly in section, of theapparatus; Fig. 2 is a sectional plan view of the apparatus shown inFig. l; Fig. 3 is a top view of a mold; Fig. i is a sectional viewthrough'a modified mold; and Fig. 5 is a sectional view of anothermodified form of die.

As shown in the drawing, the apparatus comprises a base lll pierced by aconduit ii con- `trolled by a valve i2 and leading to a vacuum pump (notshown). Resting upon the base i@ and separated therefrom by a rubbergasket l is a cylindrical containerV it provided with a neck i5 and tothe shoulder i5 of which is welded or soldered a flexible Sylphon il ofcopper or other suitable material. rihe Sylphon is welded or soldered atthe top to a plate l, which is pressed 4 upwardly by the springs i9.These springs are designed to odset the pressure of the atmosphere whenthe interior or" the container is evacuated, and to prevent prematurecompression of the dies.

5 A plunger 2li is fastened by the screw 2i to the plate i8 and ispreferably provided with an enlarged head 22.

A slight depression 25 is provided in the base i0 and within this isnested a die block 26 hav- 50 ing a depression 2l in its upper surface,within which the die 28 closely fits.

The die 28 is made of a plastic, preferably elastic, substantiallyincompressible material, preferably rubber, such as rubber known as 55squeegee rubber, and is provided with a number of cavities29 in itsupper surface. The die is preferably not of great thickness, in orderthat there will not be any appreciable sliding of the die along thesides of the die block. On the other hand, there should be an amount ofmag terial below the cavities sumcient to prevent flowage or distortionof the material.

Therefore, if the type 28a of die shown in Fig. 5 is employed, asuitable rubber washer should be applied above and below the die itself.1o

For penpoint and similar purposes a die approximately l/s of an inch inthickness is satisfactory, and the cavities may be slightly more thanone half of this thickness. A washer 30 is placed on the top of the dieand the washer may 16 suitably be about 11g of an inch thick.

The cavities in the die are made of precisely the same shape desired inthe ilnished article, but are very considerably larger than the articleitself, because of the change in the apparent 20 density of the articlewhich occurs upon compression. For most metallic powders, such astungsten, osmium, iridium, or the like, the powder is compressed toone-half to one-quarter of the original volume under the necessary pres-25 sures.

In Fig. 4 a die is shown', in which a number of different shapedcavities are provided. 29a, for example, being suitable for a phonographneedle, 29D being a cylinder, 23o a spheroid, and 30 29d a hemisphere.In making a complete sphere, two molds such as 29d may be employed,being placed together in registration in any suitable manner beforepressing.

Instead of elastic bodies, plastic inelastic materials may be employed,such as soft metal, say, lead. The use of an elastic body is greatlypreferred because the die does not have to be destroyed after one use.

The container ld is secured to the base it by fasteners 35, which arepivotally mounted at 36 and the edges 3l of which overhang the flangeSi@ on the container.

In the operation of the device, powdered metallic material is carefullysifted into the cavities 2S. In general the powder is around 100 to 300mesh. Too fine a material is likely to lower the apparent density belowthe normally desirable amount, and on the other hand, if the material istoo coarse, it will not fill the cavities uniformly, nor Will it bind aseasily. Moreover, Where a plurality of metallic materials are mixed, forexample in forming an osmium-iridium or platinum alloy, uniformity ofcomposition will not be accomplished with too large particles.

In operating with the plastic die it is, how-L Y ever, possible to useextremely line material,

` then tamped down slightly, if necessary. the

which could not be employed with .the ordinary rigid orinelastic die,such as steel. For example,

many very une powders willcreep in a steel die but will show no suchtendency with rubber.

Fior this reason, the process may be employed to form objects to apredetermined weight, even where the shape is not important. VForexample,

` where it is desired to form pellets, powder may be sifted into adepression in a plastic mold, and

tamping alwaysvbeing uniform, and then sub- Jected to pressure.. Inthis-way. it is possible to procure pellets of uniform weight -muchmorevexactly and readily than in any other known method. l

Siftingis preferred because there is no tendency to overpack or compressthe powder in spots, but a vibrator may be employed to vibrate the dieswhile the material is falling into it. This is particularly desirable incase of a cavity shaped like llc.

After the cavities have been iiiled, the uppersurfaceisscrapedwithaflatedgeandadieis` placed in the die-block II andcovered with a washer lli` A second die-block 26a is then placed on topofthe first `'die-block, the second one having a lug Il registering withthe depression 21.

' Ihe die-block IIa likewise has Aa die receiving depression 21a, inwhich a second die and washer are placed and this nesting oi' die-blocksls continued until the container is filled to the desired height. Aclosing die-block 21e is placed on top of the last die and is-Just belowthe plunger 22. A steel sleeve 4| closely fits the die-blocks and isprovided with a longitudinal groove 42 to per- -mit ready passage of airinto and out of the die-blocks.

The separate nesting of the 'dies is of impartance, because it isdesirable not to have any die move any considerable distance withrespect to the walls enclosing it. If a number of dies were piled on topof each ailier, the movement of the upper ones would be cumulative,whereas f in the present arrangement, the cumulation is taken up betweenthe die blocks.

After the diesare properly mounted the con- 1 tainer Il is placed overthem and the fasteners escasos intended. Higher pressure gives harderproducts. Under a pressure of 70 tons per square inch,

a series of 5 dies and washers Va of an inch inv thickness and 1'.' ofan inch in diameter and each containing 2| rectangular cavitiesapproximately 'H28 inch by 9538 inch. the washers being approximately ofan inch 'thick'will compress less than 56 of an inch total when lledwith metallic powder having a 3 to 1 compression ratio.

The pressure need not be maintained more than a few seconds. and afterrelease, air or other gas is admitted to the container and the resultingpellets are removed from the dies. For

smne purposes. itis desirable that the ygas be inert. such as hydrogen.

The pellets may then beitreated in any de` sired manner, for example,jbyheat treatment below the melting point for a prolonged period.l

The process is particularly suitable lfor the manufacture oi small tipsto be welded automatifcally to bases of considerably larger size,particularly pen, points, phonograph needles, meter pivots,.and thelike. In such operations, it is quite valuable to have pieces oi'predetermined and uniformsize and shape,:so that the welding operationmayproceed automatically and uniformly.

In the case of pen points, the particles are made from powdered 'penpoint material. gen- .erally of a hard, corrosion 'resistant metal oralloy, and are made of a size preferably to produce 1800 tov` 10,000pellets per troy ounce from material having a specificgravity ashigh as18.

A typical cube may have a side" oil-'.040 inch. The objects preferably.will not exceed'approxi- .mately .06'inch on a side. 4this beingapproximately 1% of an inch on a side. It is preferable 'that thefinished article does not exceed $4000 of a cubic inch in volume.

. In some instances it maybe desirable to omit the top washer or to usea washer of a rigid material. This provides a more smooth and shinysurface where the metal contacts metal.

This application is a continuation in part of .my co-pendingapplication.l'l3,036, filed November 5, 1937.

I claim:

A metallic tip for small bases vcomprising a small preformed body ofpredetermined shape, the body being not substantially more than M000 ofa cubic inch in volume and having all of its dimensions less than Vsinch, having the uni-x formity of structure and strength resulting fromcompression of finely divided metallic particles under heavy pressure ina cavity in a substantially incompressible plastic body having all ofits dimensionsless than inch, to a coherent mass of the predeterminedshape but materially smaller in volume than the cavity.

CARL PFANSTIEHL.

